Technical Field
The present disclosure relates to an external vision and/or weapon aiming and firing system for military land vehicles (such as armoured military vehicles, tanks, mine-clearance vehicles, armed land vehicles, etc.), for military aircraft (such as military aeroplanes and helicopters) and for military naval units (such as cruisers, patrol boats, corvettes, etc.).
With regard to this, the present disclosure will hereinafter be described, for simplicity, by making explicit reference only to military land vehicles without, however, any loss of generality. In fact, it is important to underline that the external vision and/or weapon aiming and firing system according to the present disclosure can also be advantageously exploited on board military aircraft and/or military naval units without having to make any substantial changes to the operation and architecture of said system.
Description of the Related Art
As is known, nowadays military land vehicles are generally equipped with indirect external vision systems, i.e. where vision of the outside surroundings captured via optoelectronic devices is made available to an operator on board the military vehicle via a user interface, which generally comprises at least one screen.
For example, such indirect external vision systems can be opportunely configured to capture video, i.e. sequences of images, of the outside surroundings in the visible spectrum (i.e. at wavelengths ranging between approximately 380/400 nm and 700/750 nm) and/or in the infrared spectrum (i.e. at wavelengths ranging between approximately 0.7/0.75 μm and 1000 μm).
In general, an external vision system of a military land vehicle comprises:                one or more video capture device(s) installed on the outside of the military land vehicle, each video capture device being configured to capture a respective video stream, i.e. a respective sequence of images, of the surroundings outside the military land vehicle, for example in the visible or infrared spectrum;        an electronic control unit installed on board the military land vehicle, connected to the video capture device(s) to receive the video stream(s) generated by said video capture device(s) and configured to process said video stream(s) and to control operation and aiming of the sensor(s); and        a user interface installed inside the crew compartment of the military land vehicle, connected to the control unit and configured to display the processed video stream(s) provided by said control unit.        
In general, the user interface comprises:                a screen configured to display the processed video stream provided by the control unit; and        user control means configured to enable an operator to control, i.e. operate, the external vision system.        
In general, the electronic control unit inserts an aiming reticle in the images of the video stream displayed by the user interface to indicate the aiming direction of the video capture device that generated said displayed video stream. In general, the aiming reticle is inserted in the images of the displayed video stream using graphical overlay techniques.
The user interface can be installed in various positions inside the crew compartment of the military vehicle, for example in the commander's station of the military vehicle.
Generally, in the case of a military vehicle equipped with a weapon, for example, in the case of a tank or an infantry combat vehicle, an external vision system is operationally associated with said weapon so as to enable an operator to control its aiming and firing, the end result being that said external vision system also acts as an aiming and firing system for said weapon. In this case:                at least one video capture device is coupled to said weapon in order to capture a video stream of the surroundings outside the military vehicle in a direction in which said weapon is aimed;        the user control means are configured to enable an operator to also control the aiming and firing of the weapon;        the electronic control unit is configured to        also control the aiming and firing of the weapon, and        insert an aiming reticle in the images of the video stream acquired from the video capture device that indicates the direction in which the weapon is aimed (and therefore also the aiming direction of said video capture device); and        the user interface can be opportunely installed inside the crew compartment of the military vehicle in an artilleryman's/gunner's station.        
The user control means can opportunely include:                a control stick or joystick configured to enable an operator to control,        in the case of a mere external vision system, the aiming of the video capture device(s), or,        in the case of an external vision and weapon aiming and firing system, the aiming of the weapon and the video capture device coupled to it; and        a push-button control panel (which, for example, could be opportunely provided on the edges of the screen or on a control panel separate from the screen), configured to enable an operator to control        operation of the external vision system (or the external vision and weapon aiming and firing system) and,        in the case of an external vision and weapon aiming and firing system, also the operation of said weapon.        
In particular, the push-button control panel could be opportunely configured to send respective commands, when operated by an operator, to the electronic control unit, which is consequently configured to control, on the basis of commands received from the push-button control panel (or, more in general, on the basis of commands imparted by an operator through the user control means), operation of                the external vision system (or the external vision and weapon aiming and firing system), and        also the weapon in the case of an external vision and weapon aiming and firing system.        
Alternatively, instead of the screen and push-button control panel, the user interface could include a touch screen configured to perform the function of both the screen and the push-button control panel.
In general, external vision and/or weapon aiming and firing systems of the above-stated type are configured to allow an operator to select the colour of the aiming reticle.
In fact, the aiming reticle colour is a parameter of fundamental importance in order to allow accurate tracking of a target and/or an element of interest. In fact, the tracking of a target could be particularly difficult in the case where the aiming reticle has a colour easily confused with that of the target (or that of the background in the displayed video stream), for example, in the case of a bright-coloured target and a white aiming reticle, or in the case of a dark-coloured target and a black aiming reticle.
As previously described, current external vision and/or weapon aiming and firing systems are configured to allow an operator to manually select the colour of the aiming reticle. Therefore, in cases where the aiming reticle colour does not allow accurate tracking of a target, an operator is forced to manually change the colour of the aiming reticle (for example, via the user control means of the user interface) in order to make it more visible with respect to the target and/or the background in the displayed video stream. However, this procedure can delay target engagement and this delay could even become fatal for those on board the military vehicle.
Furthermore, with current external vision and/or weapon aiming and firing systems, the rapid engagement of close multiple targets having opposite colour polarities can be very difficult, if not even impossible.
French patent application FR 2 699 658 A1 describes a stabilized aiming system for a weapon (for example, a rifle). In particular, the system described in FR 2 699 658 A1 includes a screen and processing circuitry that is configured to automatically change the colour or shade of grey of an aiming reticle displayed on the screen in order to obtain the best contrast possible between said reticle and the images observed. In detail, in the case of grey-scale images, the automatic modification of the aiming reticle's shade of grey is based on calculating an average of the greyscale values of the pixels positioned around the aiming reticle, where the average is weighted by the use of decreasing weights as the distance of the pixels from the reticle increases. Instead, in the case of colour images, FR 2 699 658 A1 limits itself to just affirming that the contrast improvement procedure can also be used in the case of a colour screen by introducing the use of a colour contrast matrix.
The algorithm described in FR 2 699 658 A1 is based exclusively on a modulation of the reticle's luminance value. This choice does not enable having clear vision of the reticle in certain operational scenarios.
Furthermore, it is important to note that FR 2 699 658 A1 does not actually describe any procedure for automatically changing the colour of the aiming reticle in the case of colour images, nor even teaching how it is possible to determine the colour to assign to the reticle.